Effect of apomorphine on the wakefulness-sleep cycle of the common frog Rana temporaria

Abstract

This work considers effects of introduction into spinal lymphatic sac of dopamine agonist--apomorphine-(APO) at doses of 0.1, 1.0, 2.0 and 4.0 mg/kg body weight on the common frog wakefulness-sleep cycle (WSC). Usually the frog WSC is represented by wakefulness and three types of passive-protective behavior: by immobility states of the type of catalepsy, catatonia, and cataplexy that are characterized by high thresholds of arousal and by different (corresponding to the name) skeletal musculature tones. These immoboloty forms are considered as homologues of mammalian stress-reaction, hibernation, and sleep. Low apomorphine doses produced in WSC a marked decrease of portion of wakefulness and an increase of the immoboloty state of the catalepsy; high doses, on the contrary, initially promoted in CNS an increase of wakefulness and the state of catalepsy by demonstrating thereby its stressogenic action; after this, in WSC these increased the portion of the sleep-like immobility state of the catalepsy type that is considered as a functional homologue of sleep of homoiotherms. In spectra of electrograms of the flog telencephalon the representation of waves of the delta diapason rose. Taking into account that the states of catalepsy and cataplexy in frogs are under control of the anterior hypothalamus, it can be suggested that manifestations of cataplexy (sleep) in frog are due to the low level of dopaminergic activity, whereas manifestations of catalepsy (the homologue of stress reaction) are due to the high dopamine content in the anterioi hypothalamic structures. Comparative analysis of changes in WSC of amphibians and mammals in response to administration of dopamine and its agonists allows thinking that the role of the dopaminergic neurotransmitter system in regulation of the vertebrate WSC is unanimous: the low level of activity of this system facilitates development of sleep (catalepsy), whereas the high level provides reaction of arousal and is actively included in the system providing stress-reaction.